docs: rewrite examples with var using let and const (eslint#19315)

docs/src/rules/array-callback-return.md

@@ -9,7 +9,7 @@ If we forget to write `return` statement in a callback of those, it's probably a
 
 ```js
 // example: convert ['a', 'b', 'c'] --> {a: 0, b: 1, c: 2}
-var indexMap = myArray.reduce(function(memo, item, index) {
+const indexMap = myArray.reduce(function(memo, item, index) {
   memo[item] = index;
 }, {}); // Error: cannot set property 'b' of undefined
 ```
@@ -45,17 +45,17 @@ Examples of **incorrect** code for this rule:
 ```js
 /*eslint array-callback-return: "error"*/
 
-var indexMap = myArray.reduce(function(memo, item, index) {
+const indexMap = myArray.reduce(function(memo, item, index) {
     memo[item] = index;
 }, {});
 
-var foo = Array.from(nodes, function(node) {
+const foo = Array.from(nodes, function(node) {
     if (node.tagName === "DIV") {
         return true;
     }
 });
 
-var bar = foo.filter(function(x) {
+const bar = foo.filter(function(x) {
     if (x) {
         return true;
     } else {
@@ -73,19 +73,19 @@ Examples of **correct** code for this rule:
 ```js
 /*eslint array-callback-return: "error"*/
 
-var indexMap = myArray.reduce(function(memo, item, index) {
+const indexMap = myArray.reduce(function(memo, item, index) {
     memo[item] = index;
     return memo;
 }, {});
 
-var foo = Array.from(nodes, function(node) {
+const foo = Array.from(nodes, function(node) {
     if (node.tagName === "DIV") {
         return true;
     }
     return false;
 });
 
-var bar = foo.map(node => node.getAttribute("id"));
+const bar = foo.map(node => node.getAttribute("id"));
 ```
 
 :::
@@ -98,7 +98,7 @@ This rule accepts a configuration object with three options:
 * `"checkForEach": false` (default) When set to `true`, rule will also report `forEach` callbacks that return a value.
 * `"allowVoid": false` (default) When set to `true`, allows `void` in `forEach` callbacks, so rule will not report the return value with a `void` operator.
 
-**Note:** `{ "allowVoid": true }` works only if `checkForEach` option is set to `true`.  
+**Note:** `{ "allowVoid": true }` works only if `checkForEach` option is set to `true`.
 
 ### allowImplicit
 
@@ -108,7 +108,7 @@ Examples of **correct** code for the `{ "allowImplicit": true }` option:
 
 ```js
 /*eslint array-callback-return: ["error", { allowImplicit: true }]*/
-var undefAllTheThings = myArray.map(function(item) {
+const undefAllTheThings = myArray.map(function(item) {
     return;
 });
 ```

docs/src/rules/for-direction.md

@@ -15,16 +15,16 @@ Examples of **incorrect** code for this rule:
 
 ```js
 /*eslint for-direction: "error"*/
-for (var i = 0; i < 10; i--) {
+for (let i = 0; i < 10; i--) {
 }
 
-for (var i = 10; i >= 0; i++) {
+for (let i = 10; i >= 0; i++) {
 }
 
-for (var i = 0; i > 10; i++) {
+for (let i = 0; i > 10; i++) {
 }
 
-for (var i = 0; 10 > i; i--) {
+for (let i = 0; 10 > i; i--) {
 }
 
 const n = -2;
@@ -40,10 +40,10 @@ Examples of **correct** code for this rule:
 
 ```js
 /*eslint for-direction: "error"*/
-for (var i = 0; i < 10; i++) {
+for (let i = 0; i < 10; i++) {
 }
 
-for (var i = 0; 10 > i; i++) { // with counter "i" on the right
+for (let i = 0; 10 > i; i++) { // with counter "i" on the right
 }
 
 for (let i = 10; i >= 0; i += this.step) { // direction unknown

docs/src/rules/getter-return.md

@@ -12,7 +12,7 @@ further_reading:
 The get syntax binds an object property to a function that will be called when that property is looked up. It was first introduced in ECMAScript 5:
 
 ```js
-var p = {
+const p = {
     get name(){
         return "nicholas";
     }
@@ -38,7 +38,7 @@ Examples of **incorrect** code for this rule:
 ```js
 /*eslint getter-return: "error"*/
 
-p = {
+const p = {
     get name(){
         // no returns.
     }
@@ -66,7 +66,7 @@ Examples of **correct** code for this rule:
 ```js
 /*eslint getter-return: "error"*/
 
-p = {
+const p = {
     get name(){
         return "nicholas";
     }
@@ -99,7 +99,7 @@ Examples of **correct** code for the `{ "allowImplicit": true }` option:
 
 ```js
 /*eslint getter-return: ["error", { allowImplicit: true }]*/
-p = {
+const p = {
     get name(){
         return; // return undefined implicitly.
     }

docs/src/rules/no-cond-assign.md

@@ -39,13 +39,13 @@ Examples of **incorrect** code for this rule with the default `"except-parens"`
 /*eslint no-cond-assign: "error"*/
 
 // Unintentional assignment
-var x;
+let x;
 if (x = 0) {
-    var b = 1;
+    const b = 1;
 }
 
 // Practical example that is similar to an error
-var setHeight = function (someNode) {
+const setHeight = function (someNode) {
     do {
         someNode.height = "100px";
     } while (someNode = someNode.parentNode);
@@ -62,20 +62,20 @@ Examples of **correct** code for this rule with the default `"except-parens"` op
 /*eslint no-cond-assign: "error"*/
 
 // Assignment replaced by comparison
-var x;
+let x;
 if (x === 0) {
-    var b = 1;
+    const b = 1;
 }
 
 // Practical example that wraps the assignment in parentheses
-var setHeight = function (someNode) {
+const setHeight = function (someNode) {
     do {
         someNode.height = "100px";
     } while ((someNode = someNode.parentNode));
 }
 
 // Practical example that wraps the assignment and tests for 'null'
-var setHeight = function (someNode) {
+const set_height = function (someNode) {
     do {
         someNode.height = "100px";
     } while ((someNode = someNode.parentNode) !== null);
@@ -94,27 +94,27 @@ Examples of **incorrect** code for this rule with the `"always"` option:
 /*eslint no-cond-assign: ["error", "always"]*/
 
 // Unintentional assignment
-var x;
+let x;
 if (x = 0) {
-    var b = 1;
+    const b = 1;
 }
 
 // Practical example that is similar to an error
-var setHeight = function (someNode) {
+const setHeight = function (someNode) {
     do {
         someNode.height = "100px";
     } while (someNode = someNode.parentNode);
 }
 
 // Practical example that wraps the assignment in parentheses
-var setHeight = function (someNode) {
+const set_height = function (someNode) {
     do {
         someNode.height = "100px";
     } while ((someNode = someNode.parentNode));
 }
 
 // Practical example that wraps the assignment and tests for 'null'
-var setHeight = function (someNode) {
+const heightSetter = function (someNode) {
     do {
         someNode.height = "100px";
     } while ((someNode = someNode.parentNode) !== null);
@@ -131,9 +131,9 @@ Examples of **correct** code for this rule with the `"always"` option:
 /*eslint no-cond-assign: ["error", "always"]*/
 
 // Assignment replaced by comparison
-var x;
+let x;
 if (x === 0) {
-    var b = 1;
+    const b = 1;
 }
 ```
 

docs/src/rules/no-constant-condition.md

@@ -73,7 +73,7 @@ do {
     doSomethingForever();
 } while (x = -1);
 
-var result = 0 ? a : b;
+const result = 0 ? a : b;
 
 if(input === "hello" || "bye"){
   output(input);
@@ -105,7 +105,7 @@ do {
     doSomething();
 } while (x);
 
-var result = x !== 0 ? a : b;
+const result = x !== 0 ? a : b;
 
 if(input === "hello" || input === "bye"){
   output(input);

docs/src/rules/no-control-regex.md

@@ -30,13 +30,13 @@ Examples of **incorrect** code for this rule:
 ```js
 /*eslint no-control-regex: "error"*/
 
-var pattern1 = /\x00/;
-var pattern2 = /\x0C/;
-var pattern3 = /\x1F/;
-var pattern4 = /\u000C/;
-var pattern5 = /\u{C}/u;
-var pattern6 = new RegExp("\x0C"); // raw U+000C character in the pattern
-var pattern7 = new RegExp("\\x0C"); // \x0C pattern
+const pattern1 = /\x00/;
+const pattern2 = /\x0C/;
+const pattern3 = /\x1F/;
+const pattern4 = /\u000C/;
+const pattern5 = /\u{C}/u;
+const pattern6 = new RegExp("\x0C"); // raw U+000C character in the pattern
+const pattern7 = new RegExp("\\x0C"); // \x0C pattern
 ```
 
 :::
@@ -48,14 +48,14 @@ Examples of **correct** code for this rule:
 ```js
 /*eslint no-control-regex: "error"*/
 
-var pattern1 = /\x20/;
-var pattern2 = /\u0020/;
-var pattern3 = /\u{20}/u;
-var pattern4 = /\t/;
-var pattern5 = /\n/;
-var pattern6 = new RegExp("\x20");
-var pattern7 = new RegExp("\\t");
-var pattern8 = new RegExp("\\n");
+const pattern1 = /\x20/;
+const pattern2 = /\u0020/;
+const pattern3 = /\u{20}/u;
+const pattern4 = /\t/;
+const pattern5 = /\n/;
+const pattern6 = new RegExp("\x20");
+const pattern7 = new RegExp("\\t");
+const pattern8 = new RegExp("\\n");
 ```
 
 :::

docs/src/rules/no-dupe-args.md

@@ -25,7 +25,7 @@ function foo(a, b, a) {
     console.log("value of the second a:", a);
 }
 
-var bar = function (a, b, a) {
+const bar = function (a, b, a) {
     console.log("value of the second a:", a);
 };
 ```
@@ -43,7 +43,7 @@ function foo(a, b, c) {
     console.log(a, b, c);
 }
 
-var bar = function (a, b, c) {
+const bar = function (a, b, c) {
     console.log(a, b, c);
 };
 ```